OsMYBdt1 Enhances Drought Tolerance in Rice via Antioxidant Defense and ABA Signaling

Abstract Rice production is severely constrained by drought stress, which is increasingly exacerbated by climate change. Here, we functionally characterized OsMYBdt1, a previously unstudied MYB transcription factor in rice. CRISPR/Cas9-mediated osmybdt1 knockout mutants exhibited severe drought hypersensitivity, whereas OsMYBdt1-overexpressing (OX) lines demonstrated robustly enhanced tolerance at both vegetative and reproductive stages. Mechanistically, OsMYBdt1 acts as a pivotal regulatory node integrating reactive oxygen species (ROS) homeostasis and abscisic acid (ABA) signaling. Under drought, OsMYBdt1 reinforces the antioxidant network by boosting superoxide dismutase (SOD) and peroxidase (POD) activities, thereby accelerating ROS scavenging. Concurrently, it modulates ABA-dependent stomatal closure to restrict transpirational water loss. The drought-susceptible phenotype of osmybdt1 was fully rescued by exogenous ABA. At the molecular level, molecular docking combined with dual-luciferase transactivation assays elucidated that OsMYBdt1 binds to and transcriptionally activates the promoter of OsRab16A, a Group-2 Late Embryogenesis Abundant gene. Furthermore, haplotype analysis uncovered two major natural variants of OsMYBdt1 exhibiting distinct geographic and ecotypic distribution patterns between indica and japonica subspecies, underscoring its evolutionary divergence under environmental selection. Collectively, our study characterizes OsMYBdt1 as a central regulatory node and provides valuable genetic resources for breeding drought-resilient rice cultivars.